1. Field of the Invention
The present invention relates generally to control systems associated with a mechanical press machine, and, more particularly, to an auxiliary control system arranged for use with a programmable logic controller to provide a dedicated, high-performance press controller.
2. Description of the Related Art
Mechanical press machines operate in an industrial environment in which high levels of power transfer are needed over relatively short processing intervals to deliver high impact shaping forces that act through the die assembly to machine an attached workpiece. Machining operations of this type require a control mechanism that monitors the condition of various parts of the press machine and undertakes whatever corrective action is deemed necessary in the event that any abnormal, substandard, or other impermissible conditions arise either in the functioning of the individual devices of the press machine or in the processing activity involving the die assembly and integral workpiece. Some of the critical features for any such control mechanism include near-instantaneous access to and retrieval of monitoring data, rapid processing of the data to arrive at a control decision, and implementation of the decision within a time frame suitable for preserving the press machine against any irreparable harm or other forms of damage materially affecting the integrity of the machine and its operation. This window of protection clearly depends upon the speed of the press, with press running speeds on the order of 400 strokes per minute (spm) necessitating very short intervals of response. The responsiveness to error detection takes on added importance in situations involving press conditions that progressively worsen in the absence of any countermeasures such as when the die members are mispositioned or misaligned, leading to eventual destruction of the workpiece and die assembly that can be averted only if an immediate shutdown is ordered.
The complexity and speed of the tasks that fall to the press controller for their precise and automatic execution suggests a computer-based implementation in order to take advantage of the processing power, data management, and digital control available with microprocessor control apparatus. The complexity of press operation, in particular, usually becomes a vital focus of the engineering effort and typically leads to a press control design based on a general purpose programmable logic controller (PLC). In one representative PLC arrangement, the PLC processor will issue control commands to the clutch control circuit based upon a logic operations analysis of a group of performance measurements obtained from sensors which detect certain performance indicia (e.g., crankshaft angle) representing the operating condition of the press machine. The clutch control circuit directly controls the clutch valves in accordance with its control state as determined by the control commands issued by the PLC. In this manner the PLC can cause the clutch valves to become deactivated, leading to a disengagement of the flywheel and an accompanying stoppage in the slide motion. However, conventional PLC arrangements suffer from a variety of limitations that affect their ability to adequately manage the control activity and meet the real-time demands of high speed machines.
A typical PLC arrangement employs a backplane to serve as the communications bus for interconnecting the PLC processor with the array of individual input/output devices with which the processor interacts in terms of receiving input data for use in executing the control program and transmitting control data for use in controlling the targeted objects. In a machine application, the input devices would encompass the sensors deployed within the press machine and die assembly while the output devices would include the actuators and other control apparatus (e.g., clutch control circuit) arranged to control corresponding machine parts (e.g., clutch assembly). However, for purposes of press machine applications, backplane communications are not sufficiently fast to handle either the transfer of monitoring information from the sensors to the PLC processor or the transmission of logic control data from the PLC processor to the actuator assembly within the time window needed to accomplish real-time processing. Other factors which contribute to the processing delay of the PLC include the clock speed and the execution time of the control program, which increases in a manner commensurate with the size and number of logic operations programmed for execution by the PLC processor.
These features of the conventional PLC arrangement affecting processing speed come together to establish a response window that defines how fast the PLC can analyze the operating condition of the press machine and then implement control decisions in a manner that provides some level of meaningful synchronism between the detection of a press operating event and the controlled response tailored to the detected event. Though possibly adequate at relatively low speeds, conventional PLC arrangements nevertheless become seriously ineffective at higher operating speeds when the machine demands a narrower response window than the PLC can deliver. Consequently, when the response time is too slow, this means that the PLC processor, among other possibilities, is considered to have missed the occurrence of a critical operating event (e.g., a crankshaft malfunction indicated by an out-of-bound crankshaft angle sensor measurement); responded to the operational crisis in an untimely manner that negated any meaningful impact upon press operation; or responded with a control command that no longer harmonizes with the current condition of the machine because of rapid changes in the machine activity that went undetected by the PLC during the intervening processing period. What is therefore needed is a press controller that enables a more rapid coordination and execution of tasks aligned with monitoring the condition of the press machine and implementing the control decisions derived from an evaluation of the monitoring information.
According to one embodiment of the present invention there is provided an auxiliary control system operatively associated with a press controller which is arranged to control a press machine. The press controller comprises a programmable logic controller including a main processor. The auxiliary control system includes a sensor assembly arranged to provide sensor information which is representative of the condition of the press machine and a die assembly disposed within the press machine. A monitoring device provided in the form of an auxiliary processor is arranged to monitor for the occurrence of press operating events as signified by the sensor information. The auxiliary processor provides a state signal which is representative of the results of the monitoring activity, namely whether one of the press operating events was detected and an indication of which one(s). The press operating events preferably relate to the functioning of the crankshaft from which a measurement of the crankshaft angle is obtained by the sensor assembly. The state signal is provided to the press controller to enable it to take the appropriate control action based upon the state signal.
According to another embodiment of the present invention there is provided a programmable logic controller for use in controlling a press machine. The programmable logic controller includes a main processor and is operatively associated with an actuator assembly arranged to control devices of the press machine in accordance with a control state thereof. The programmable logic controller (PLC) further includes an auxiliary sensor assembly for providing sensor information which is representative of the condition of the press machine and a die assembly disposed within the press machine. An auxiliary logic processor is arranged to perform logic operations in respect of the sensor information and to generate control signals based upon the logic operations performance results for use in controlling the press machine. An auxiliary output device is arranged to interface the auxiliary logic processor with the device control assembly to enable communication therebetween.
Among other advantageous features, both of the stated embodiments avoid using the backplane of the programmable logic controller in transmitting sensor information from their respective sensor assemblies to their respective processing modules. Additionally, both embodiments perform their respective evaluation activities with respect to the sensor information independently of the control program associated with the operation of the PLC main processor.
The invention, in one form thereof, comprises a control system for use with a press machine. The control system includes a press controller arranged to control the press machine, such press controller comprising a programmable logic controller including a main processor; a sensor means for providing sensor information representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; an auxiliary processor arranged to monitor for the occurrence of at least one press operating event as signified by the sensor information provided by the sensor means and to provide a state signal representative of the results of the monitoring activity; and a means for providing the press controller with the state signal provided by the auxiliary processor to enable the press controller to control the press machine based, at least in part, upon the state signal. At least one of the at least one operating event defines a non-allowable operating state for the press machine. The press controller effects a termination of press machine operation in response to a state signal from the auxiliary processor which indicates the occurrence of an operating event associated with a non-allowable operating state.
There is further provided a connection means for providing a communications path between the sensor means and the auxiliary processor, wherein the connection means is discrete from a signal bus defining, at least in part, a backplane of the programmable logic controller.
The invention, in another form thereof, comprises a system for use in a press machine and operatively associated with a press controller arranged to control the press machine. The system includes, in combination, a sensor means for providing sensor information representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; a monitoring means for monitoring for the occurrence of at least one press operating event using the sensor information provided by the sensor means and for generating a state signal representative of the results of the monitoring activity; and a means for providing the press controller with the state signal generated by the monitoring means to enable the press controller to control the press machine based, at least in part, upon the state signal.
At least one of the at least one operating event defines a non-allowable operating state for the press machine. The sensor information provided by the sensor means includes a measure of the crankshaft angle for the press machine. Additionally, the sensor information provided includes a measure of some other press machine condition, wherein one of the at least one press operating event associated with a non-allowable operating state defines unacceptable values for the press machine condition for the measured crankshaft angle.
The press controller further comprises a programmable logic controller including a main processor, while the monitoring means further comprises an auxiliary processor. The action of the auxiliary processor in conducting the monitoring activity relative to the at least one operating event is independent of the programmable logic controller.
The invention, in another form thereof, includes a system for use in a press machine and operatively associated with a programmable logic controller arranged to control the press machine and including a main processor. The system comprises, in combination, a sensor means for providing sensor information representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; an auxiliary processor means for evaluating the sensor information provided by the sensor means according to evaluation criteria associated with the operation of the press machine and for providing a state signal representative of the evaluation results; and a means for communicating the state signal provided by the auxiliary processor means to the programmable logic controller to enable control of the press machine by the programmable logic controller based, at least in part, upon the state signal.
The evaluation criteria associated with the operation of the auxiliary processor means incorporates representations of at least one press operating event for the press machine. The evaluation performed by the auxiliary processor means monitors for the occurrence of the at least one press operating event and provides an event indicator in the state signal when the occurrence of an operating event is detected. At least one of the at least one press operating event defines a non-allowable operating state for the press machine.
The system further comprises a connection means for providing a communications path between the sensor means and the auxiliary processor means, wherein the connection means is discrete from a signal bus defining, at least in part, a backplane of the programmable logic controller.
The invention, in another form thereof, comprises a method of controlling a press machine, the method operatively associated with a press controller arranged to control the press machine. The method includes the steps of sensing the condition of at least one of the press machine and a die assembly disposed within the press machine and generating sensor information representative thereof; monitoring the generated sensor information for the occurrence of at least one press operating event as signified by the sensor information and providing a state signal representative of the results of the monitoring activity, wherein at least one of the at least one press operating event defines a non-allowable operating state for the press machine; and providing the state signal to the press controller to enable control of the press machine in accordance therewith. The press controller further comprises a programmable logic controller including a main processor. The monitoring step further comprises the step of providing an auxiliary processor arranged to receive the sensor information and to perform the press operating event monitoring activity, wherein the action of the auxiliary processor in performing the monitoring activity relative to the at least one operating event is independent of the programmable logic controller.
The invention, in another form thereof, includes a method of controlling a press machine, the method operatively associated with a press controller, the press controller comprising a programmable logic controller arranged to control the press machine and including a main processor. The method comprises the steps of: providing a sensor assembly to detect the operating condition of at least one of the press machine and a die assembly disposed within the press machine and generating sensor information representative thereof; evaluating the generated sensor information according to evaluation criteria associated with the operation of the press machine and providing a state signal indicative of the results of the evaluation activity; and providing the state signal to the press controller to enable control of the press machine in accordance therewith.
The evaluation step further includes the step of monitoring for the occurrence of at least one press operating event as signified by the generated sensor information, wherein at least one of the at least one press operating event defines a non-allowable operating state for the press machine. The evaluation step even further includes the step of providing an auxiliary processor arranged to receive the sensor information and to perform the evaluation activity. The action of the auxiliary processor in performing the evaluation activity relative to the generated sensor information is independent of the programmable logic controller.
The invention, in another form thereof, comprises an auxiliary control system for use with a press machine, such auxiliary control system associated with a press controller arranged to control the press machine, such press controller including an actuator assembly arranged to provide control of devices of the press machine in accordance with control signals applied thereto and further including a programmable logic controller arranged to operatively control the actuator assembly, such programmable logic controller comprising a host processor having an executable control program associated therewith. The auxiliary control system comprises, in combination, an auxiliary sensor assembly for providing sensor signals representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; an auxiliary logic processor, operatively associated with a control function defining logic operations, for carrying out the logic operations in relation to the sensor signals provided by the auxiliary sensor assembly to generate therefrom control signals enabling control of the press machine; and an auxiliary output device arranged to interface the auxiliary logic processor to the actuator assembly. The press machine control activity performed by the auxiliary logic processor is independent of the executable control program associated with the operation of the host processor of the programmable logic controller. The auxiliary logic processor, in one form thereof, further includes a logic circuit.
The actuator assembly, in one form thereof, further comprises a clutch control circuit arranged to control a clutch assembly of the press machine and having a signal input side and a signal output side. The clutch control circuit, in one form thereof, includes a relay assembly having control inputs and control outputs and operatively arranged to provide clutch control signals along the control outputs thereof in dependence upon the state of the control inputs thereof. The clutch control circuit, in another form thereof, includes an output means for providing an interface between the host processor of the programmable logic controller and the clutch assembly and having signal inputs and signal outputs, the output means responsive to the state of the signal inputs thereof as determined by the host processor for applying clutch control signals on the signal outputs thereof to the clutch assembly. The auxiliary logic processor, in one form thereof, is arranged to communicate directly with the clutch assembly.
The invention, in yet another form thereof, comprises a programmable logic controller for use in controlling a press machine, such programmable logic controller operatively associated with a machine control assembly arranged to provide control of devices of the press machine in accordance with the control state thereof, the programmable logic controller including a central processor for executing a control program in relation to input data to generate control data based upon the control program execution results for use in controlling the press machine. The programmable logic controller further comprises an auxiliary sensor means for providing sensor information representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; an auxiliary processor means for executing an auxiliary control function in respect of sensor information provided by the auxiliary sensor means to provide control information based upon the auxiliary control function execution results for use in controlling the press machine; and an auxiliary output means for applying control signals representative of the control information provided by the auxiliary processor means to the machine control assembly to enable control of the press machine.
The press machine control activity performed by the auxiliary processor means is independent of the control program associated with the operation of the central processor. The auxiliary control function associated with the operation of the auxiliary processor means includes logic operations.
There is further provided an auxiliary connection means for connecting the auxiliary processor means to the auxiliary sensor means and for connecting the auxiliary processor means to the auxiliary output means, wherein the auxiliary connection means is discrete from a signal bus defining, at least in part, a backplane of the programmable logic controller.
The machine control assembly, in one form thereof, further comprises a clutch control circuit arranged to control a clutch assembly of the press machine and having a signal input side and a signal output side. The clutch control circuit, in one form thereof, further includes an output means for providing an interface between the central processor and the clutch assembly and having signal inputs and signal outputs, the output means responsive to the state of the signal inputs as determined by the central processor for applying clutch control signals on the signal outputs thereof to the clutch assembly. The auxiliary processor means, in one form thereof, is arranged to communicate directly with the clutch assembly.
The invention, in yet another form thereof, comprises a control system for use in controlling a press machine. The control system includes, in combination, a device control assembly, including an actuator assembly, arranged to provide control of devices of the press machine in accordance with a control state thereof; a data means for providing press monitoring information representative of the condition of the press machine; and a programmable logic controller arranged to operate the device control assembly. The programmable logic controller comprises, in combination, a main processor operatively associated with an executable control program; an input/output means for interfacing the main processor with the data means and for interfacing the main processor with the device control assembly; and a signal bus defining, at least in part, a backplane of the programmable logic controller for connecting the main processor with the input/output means. The programmable logic controller further comprises, in combination, an auxiliary sensor means for providing sensor information representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; an auxiliary processor means for performing logic operations with respect to the sensor information provided by the auxiliary sensor means to provide control information based upon the logic operations performance results for use in controlling the press machine; and an auxiliary output means for interfacing the auxiliary processor means to the device control assembly. The press machine control activity performed by the auxiliary processor means is independent of the executable control program associated with the operation of the main processor.
The control system further includes an auxiliary connection means for connecting the auxiliary processor means to the auxiliary sensor means and for connecting the auxiliary processor means to the auxiliary output means, wherein the auxiliary connection means is discrete from the signal bus. The auxiliary sensor means, in one form thereof, is discrete from the data means.
The invention, in still yet another form thereof, comprises a programmable logic controller for use in controlling a press machine, the programmable logic controller operatively associated with a device control assembly arranged to control devices of the press machine in accordance with a control state thereof. The programmable logic controller comprises, in combination, a main processor; an auxiliary sensor means for providing sensor information representative of the condition of at least one of the press machine and a die assembly disposed within the press machine; an auxiliary logic processor means arranged to perform logic operations in respect of the sensor information provided by the auxiliary sensor means and to generate control signals based upon the logic operations performance results for use in controlling the press machine; and an auxiliary output device arranged to interface the auxiliary logic processor means with the device control assembly to enable communication therebetween.
The press machine control activity conducted by the auxiliary logic processor means is independent of an executable control program associated with the operation of the main processor.
One advantage of the present invention is that the problems heretofore associated with PLC backplane communications are avoided by an auxiliary control system arrangement in which sensor information is communicated directly to the data processing module.
Another advantage of the present invention is that the dedicated operation of the auxiliary control system vis-à-vis its functional role as a die protection module enhances the control performance of the overall press controller and facilitates a more rapid response to the detection of adverse press operating events.
Another advantage of the present invention is that the auxiliary control system can execute its logic processing and other evaluative operations and then implement the control decisions independently of the host control program associated with the operation of the PLC main processor.
Another advantage of the present invention is that the auxiliary control system may be used in one configuration to report to the PLC main processor with information detailing the condition of the press machine (which the PLC may use to control the press machine) or, in an alternative configuration, to act independently of the PLC main processor and provide direct control of the press machine.